What was the city of st. petersburg called during the soviet period?

St. Petersburg, which is Russia's second largest urban area, was founded in 1703 by the czar Peter the Great. In 1914, the German sounding name was changed to Petrograd. Then, after the death of Vladimir Lenin in 1924, the Soviet Union changed the city's name to Leningrad. Leningrad became St. Petersburg again 67 years later when the Soviet Union collapsed in 1991. 

The natural habitat around them